Reaction products formed in early age cement pastes with granulated blast furnace slag exposed to accelerated CO2 ingress

Durability and sustainability have gained an increasing importance over the last years. The production of ordinary Portland cement (OPC) has a significant impact on the CO2 emission and more eco-friendly alternatives, or supplementary cementitious materials (SCMs), as a partial replacement of the clinker in OPC are desirable and already common in use. Despite the growing gain of the production and consumption of cement with SCMs over pure OPC, more research is needed to completely understand the evolution of the microstructure of young cement pastes exposed to environmental attack, such as CO2 ingress, to estimate more accurately the impact of the early removal of formwork or short curing periods on the durability of concrete structures. To investigate the extent of carbonation, hydration and carbonation products of cement pastes with two replacement levels of ground granulated blast furnace slag (GBFS) and exposed after 3, 7 and 28 days of sealed curing to accelerated CO2 ingress were investigated by Attenuated Total Reflection Fourier Transform InfraRed spectroscopy (ATR-FTIR). When GBFS is used, irrespective of the replacement level, the carbonation of the calcium silicate hydrates (C-S-H) after 3 days sealed curing evolves similarly. For longer curing periods, the decalcification of C-S-H is slowed down by decreasing the replacement level by GBFS.status: Published onlin